Diesel generators contribute to a large share of power generation in developing countries like Peru, the Philippines and Tanzania. This leads to high costs for electricity and causes harmful air pollution. In contrast to that renewable energies can provide affordable and environmentally sound power. This paper indicates that a potential of at least 500 MW is available for upgrading isolated diesel grids to hybrid grids. A geographic analysis is developed in order to localize isolated diesel grids. Furthermore, detected diesel grids are analyzed in terms of installed capacity, operators and purpose of supply. The methodology presented in this paper enables to reveal the huge potential that retrofitting isolated diesel grids provides for the introduction of renewable energies.